Time limit relay



March 14, 1933. P. c. WARD 1,901,617

NNNNNN OR Pa frz'c/K 63 Ward Patented Mar. 14, 1933 PATENT OFFICEPATRICK G. WARD, OF HOMEVILLE, PENNSYLVANIA TIME LIMIT RELAY Originalapplication filed December 7, 1928, Serial No. 324,543. Divided and thisapplication filed November 1, 1929.

This application is a division of my application Serial No. 324,543,filed December 7 1928.

I This invention relates to time-limit control devices for controllingthe extent of rotation of motors operating the feeding mechanism forreciprocating devices, such as are found in planers, shapers, saw millsor the like. I

An object of the invention is to provide means for controlling the feedoperation of a reciprocating device to effect a definite movement of thedevice to anew position at the end of a stroke by regulating to a highdegree of accuracy the number of revolutions of the feed motor for eachoperation.

A further object of this invention is the provision of a retardingdevice especially adapted to control the time of closureof an electriccircuit by an electric switch.

Another object of the invention is the provision of a time-limit relaydesigned to automatically and exactly synchronize its own deenergizationwiththe starting of the device controlled by the relay.

A more specific object of the invention is the provision of a time-limitrelay wherein the flux distribution in the relay core may be varied;wherein the load-setting, that is, the retarding force on the relaycore, may be adjusted to any predetermined value; wherein the totaldistance of travel of the relay core may be definitely adjusted byturning one of the cooperating members of the time-element or retardingdevice; and wherein means are provided in the retarding device forgiving a quick action after a predetermined interval of time, asdetermined by the setting of adjustment of the distance 40 of travel ofthe relay core.

For a specific application of the invention. herein presented, attentionis called to applicants copending application, Serial No. 324,543, filedDecember 7, 1928, of which 45 this application constitutes a division.

In practicing my invention, I provide a relay of the solenoid typehaving a magnetizable core member and a pair of concentric windings. Theouter of the two wind- 50 ings constitutes the compensating windingSerial No. 404,065.

and is adapted to be inserted in the load circuit of the electric devicethe relay is designed to control. The number of turns of thecompensating winding in relation to the inner winding and the devicecontrolled is so adjusted that the deenergization of the time-limitrelay takes place in exact synchronism with the beginning of operationof the device controlled. A cylindrical dashpot is mounted adjacent thecoil provided with a loosely fitting piston secured by a stem to therelay core. The dash-pot cylinder is provided with an elongated orifice,the opening of which is varied by a cup-shaped member fitting over theorificed end of the dash-pot cylinder. The core-end remote from the stemis provided with an adjustable rin for varying the total distance oftravel of the piston.

The novel features of this invention will be definitely indicated in theclaims appended hereto, while the features of construction and the modeof operation will be understood b reference to the following descriptionta *en in connection with the accompanying drawing which shows thepreferred embodiment of this invention and in which:

Figure 1 is a vertical sectional view of my improved time-limit relay.

Fig. 2 is an enlarged somewhat diagrammatic sectional view taken alongthe lines IIII of Fig. 1, showing in detail the outlines of the intakeand exhaust orifices in the dash-pot and the manner in which themovement of the adjustable cap member varies the effective area of theintake orifice, and

Fig. 3 is a vertical sectional view showing a modification of thedash-pot shown in l teferring now to the drawing and particularly toFig. 1, the control relay comprises an electromagnet 48, having amovable core or plunger 49, which may be utilized to effect the openingof any circuit controlling switch, such as indicated. at 50. In thisinstance only a single-contact switch has been shown, but it will bereadily understood that as many contact members may be provided on theswitch as may be required for performing the necessary controloperations.

The electromagnet 48, in addition to the movable plunger 49, comprisesan operating coil 51, which may be energized to actuate the plunger 49to the raised position as shown. The operating coil 51 may be of theusual form-wound type, supported in the position shown, by means ofmetal brackets 52 and 52, which are bolted to the base member 53, in anysuitable manner.

In order to provide for controlling the time required for the relayplunger 49 to fall from a raised position as shown in the drawing, to apoint at which the switch 50 is actuated in response to thedeenergization of the operating coil 51, a dash pot 54 is utilized. Itwill be readily understood, that, since the plunger 49 when released bythe coil 51 is influenced by the force of gravity alone, the timeelement will depend upon the weight of the plunger and the distance itmust fall to the full open position. WVithout any dash pot or retardingmeans exerting a restraining force in opposition to the force of gravitya minimum time element is obtained which,in most instances, is of tooshort a duration to be of any practical value.

In this embodiment of the invention, the dash pot 54 is so arranged thatthe time element of the relay may be readily adjusted between relativelywide limits. As shown, the dash pot 54 comprises a cylinder member 55which may be secured to the base member '53 in any suitable manner. Thebore of the cylinder 55 is provided with a liner 56 which is adapted toreceive a piston member 57. The piston 57 is preferably formed of thesame material as the liner 56, and may be fitted to the bore withconsiderable clearance for a purpose which will be described in detailhereinafter.

As shown, the piston 57 is connected to the plunger 49 by means of asuitable connecting member 58. I

In order to limit the downward travel of the plunger and piston, theconnecting member 58 is provided with a shoulder portion 59, which inits lower position engages the upper bracket member 52. As will bereadily understood the upward movement of the plunger and piston islimited by a shoulder portion formed by the upper end of the plunger 49which is disposed to engagethe upper bracket member 52, as shown.

In order to control the operation of the dash pot 54 to vary the lengthof the time element from minimum to maximum values,

the dash pot is provided with a rotatablecap member 60, as shown. Thecap member 60 rests firmly upon the top of the dash pot cylinder 55, andis held in position by means of a set screw 61 which engages a groove 62extending circumferentially aroundthe outside periphery of the cylinder55. I

In order that a control fluid-such as air,

may be drawn into the cylinder in response to the downward movement ofthe piston 57, the cylinder top is provided with an elongated intakeorifice 63. As shown the intake orifice 63 communicates between theinterior of the cylinder 55, and the outside air through a passagecomprising a recessed portion 64 in the face of the cap member 60 and acentral opening 65.

Referring to Fig. 2, it will be. observed that the recessed portion ofthe cap member 60 is of circular shape, and positioned eccentrically,with respect to the center of the cap. It will be readily understoodthat the effective area of the intake orifice 68 may be varied, byrotating the cap member 60 to the various positions designatedas a to g,inclusive, as shown. Due to the eccentricity of the recessedportion 64,very small changes in the effective area of the intake orifice may beobtained by rotating the cap member 60, which provides for a fine andaccurately controlled adjustment of the time element of the relay.

In describing the operation of the relay it may be assumed that theoperating coil 51 is energized. In this instance the plunger 49 is heldin the up position, as shown. \Vhen the plunger is released by the coil51, the force of gravity immediately effects its movement in a downwarddirection. Consequently the dash-pot piston 57 is pulled downwardly andcreates a partial vacuum in the cylinder 55. In accordance. with a wellknown principle; the control fluid which is preferably of gaseousnature'such as air is caused to fiow into the cylinder through thecentral opening 65, passage 64, and intake orifice 63.

It will be readily understood, that the 7 restraining force exerted uponthe plunger 49, by the piston 57, will depend upon the rate with whichair enters the dash-pot cylinder 55. Since the size of the intakeorifice 63 may be readily adjusted, it is evidentthat the rate withwhich air enters the cylinder, and consequently the restraining forceexerted by the piston, against the force of gravity, may be varied toprovide the desired time element by adjusting the cap member'60 in theproper position as described in detail hereinbefore.

As stated hereinbefore, a definite amount of clearance may be providedbetween the piston 57, and the cylinder liner 56, in order that acertain amount of air may escape from the cylinder through thecylindrical passage thus formed. It will be readily understood that theair in this passage, provides an air cushion between the piston, and thecylinder walls, and functions in many respects as a lubricant.

It will be evident that the air cushion thus formed performs a functionwhich would not be possible to obtain from the use of an ordinarylubricant, since the viscosity of any lubricant necessarily varies inaccordance with temperature conditions, causing an appreciable variationof the friction force. Furthermore, the absence of lubricant in thedash-pot cylinder prevents the collection of dust particles, which, ifallowed to remain and collect upon the cylinder walls, would seriouslyinterfere with the accurate adjustment and operation of the relay.

In some instances, auxiliary means for controlling the time element ofthe relay may be required, when even the smallest movement of the capmember 60 effects too great a change in the time element. In order toprovide for an auxiliary adjusting means, provision is made for varyingthe total distance which the plunger must fall when released by'the coil51, thus interposing a distance time element upon the time elementproduced by the dash pot 54. In this instance thedistance time elementmay be controlled by utilizing an adjusting nut 66, which isdisposed toengage a threaded portion of theplunger 49 as shown. It will be readilyunderstood that the adjusting function is performed byutilizing a plate69 of paramagneticv metal, which may be adjustably secured to the bottomside of the lower bracket 52, in any suitable manner.

In some instances, the intake orifice 63 may be nearly closed to providea relatively long time element. Accordingly the upward movement of thepiston member 57, in, response to the coil 51, compresses the aircontained in the dash pot cylinder 55 and establishes a back pressurewhich mayinterfere with the resetting operation of the relay. In orderto provide for reducing the pressure set up by the piston 57, thecylinder head is provided with an exhaust port 71, which is controlledby a suitable check valve 72. As will be readily understood, thepressure-of the air inside the dash pot cylinder 55 raises the checkvalve 72, permitting the air to escape to the outside, through thepassage formed by the recess 64 and central opening 65..

In order to prevent dust particles and other foreign matter from beingcarried into the dash pot chamber by the air which enters the cylinderupon the down stroke of the piston 57, the cap member 60 is providedwith a screen 73, as shown. r I

It will be observed that a passage 74 is provided .in the dash potcylinder 55 in a position directly abovethe top of the piston 57, whenin its lowermost position. This port provides for quickly releasing thepiston when it is near its open position, and insures that the plunger49 will always drop to the full open position to effect the operation ofthe switch 50.

It will be readily understood that the design of the dash pot54 as shownin Fig. 1 may be changed to effect the control of the intake fluid invarious other ways, such for example, as shown in Fig. 5. It will beobserved, that this modification is the same as that shown in Fig. 1,with the exception, that the cylinder head is provided with a singleconical-shaped port 75, which is controlled by means of a spring-biasedvalve 76, supported and controlled by the cap member 77, "In thisinstance, the size of the intake orifice may be varied by rotating thecap member 77, which is in threaded engagement with the dash potcylinder 78, as shown. A plurality of screened air passages 79 areprovided in the top of the cap member 77 for permitting airto flow .intothe dash pot cylinder in response to the suction created 18% thedownward movement of the piston In the operation of the relay as shownin this modification, it will be readily understood, that the upwardmovement of the piston 80 compresses the air in the dash pot cylinderand effects the opening of the valve 76 which permits the escape of airquickly from the cylinder, through the passages 79, to the outside. Theupward movement of the valve member 76 may be limited by means of a capscreen 82, as shown. When the piston comes to rest, the valve 76.immediately closes under the action of its biasing spring 81, andregulates the size of the intake orifice in accordance with the'adjustedposition of the cap member 77.

The load current of one of the electric devices, such as apair of motorscontrolled b the time-element. relay passes through the compensatingcoil 7 O and thus provides means for maintaining the speed of operationof the motors or other devicein a constant predetermined ratio. It willbe readily understood, that under some operating conditions, the load onthe motor, having coil in its circuit, will vary from time to time eventhough the motor be performing the same operation. This variation inload is due to several causes, the 'most important of which are machinefriction and unbalanced load. The friction load of the machine driven bythe motor having coil 70 in "the load linewill vary in accordance withthe temperature and well-known factors,

' cap-member rotatably mounted upon said lay may be synchronized withthat of the exerted by the compensating coil without changing thesetting of the dash pot.

It may be stated in conclusion, that, while the illustrated exampleconstitutes a practical embodiment of my invention, I do not wish tolimit myself strictly to the exact details herein illustrated sincemodifications of the same may be made Without departing from the spiritof the invention as defined in the appended claims.

I claim as my invention:

1. Inna time-limit relay, in combination, a, switch-actuating plunger, acoil for raising the plunger, said plunger beingdisposed to fall freelyunder the influence of the force of gravity when released by the coil,an air dash-pot being provided with a piston disposedto retard theplunger when falling under the influence of gravity, said dash-pot beingprovided with a rotatable cap member'for regulating the flow of air intothe dash-pot, and pressure actuated means disposed to permit a readyescapement of air from the dash-pot when the piston is moved upwardly,said means being closed by the force of gravity when the piston isstoppedin any position.

2. In a time limit relay, in combination, a plunger, a coil for liftingthe plunger, said plunger being disposed to fall freely to apredetermined lower position under the infiuence ofgravity when releasedby the coil, a dash-pot for controlling the downward movement of theplunger when released by the coil, said dash-pot comprising a stationarycylindrical member provided with an air intake orifice, a piston membersecured to the plunger, said piston having a solid top surface wherebyair is drawn through the intake orifice in response'to the downwardmovement of the piston, and a rotatably mounted cap member carried bythe cylindrical member for varying the effective area-of the intakeorifice of the cylindrical member, thereby to control the time requiredfor the plunger and piston to fall to said predetermined lower position.

3. In a time-limit relay, in combination, a plunger, a coil for liftingthe plunger, said plunger being disposed to drop under the infiuence ofgravity when released by the coil, a dash-pot connected to the plungerfor retarding its movement under the action of gravity, said dash-potbeing provided with an orifice for the admission of air, and a dash-pot,said cap member having a face portion provided with an eccentricdepression disposed to cut off different sections of the orifice. 7

4. timedimit relay", comprising a; plunger, a coil for raising theplunger, an adjustable member at one end of the plunger for fixing theupper'limit of travel of the plunger, a dash-pot cylinder mountedadjacent the other end ofthe plunger, a loosely fitting piston in thecylinder, a stem connecting the plunger and piston, a shoulder on thestem for fixing the lower limitof travel of the piston, said cylinderbeing provided with an opening in the side-wall of thecylinder a shortdistance above the lower limit of travel of thepiston to prevent anyfurther'retardation of the piston after it passes, in its downwardmovement, a predetermined point above its lowermost position, anelongated radially disposed aperture in the cylinder-head, a-cup-shapedmember rotatably mounted on the -cylinder-' head, a circumferentialgroove on the outer wall of the cylinder, a set-screw in the cupshapedmember cooperating with the groove to thereby hold the cup-shaped memberin closely fitting relation with the cylinder said cup-shapedmemberhaving a circular eccentrically positioned recess adjacentthecylinder-head, and a central opening com-J munioating with the recesswhereby the size of the aperture may be accurately varied by therotation of the cup-shaped memberjto adjust'to a high degree ofaccuracythe time element of the relay. I x 1 f 5. A control device foran electric motor comprising a support, a relay of the solenoid typemounted thereon including a plunger, a main coil, an auxiliary coilconductively associated with the load circuit of the motor and designedto prevent deenergization of the relay before the starting ofthe motor,means on the relay for varying the flux distribution thereof, a dash-potcylinder mounted on' the support, a piston loosely fitting into thecylinder, a stem connecting the piston and plunger, said plunger beingprovided with a shoulder for engaging an element of the support to fixthe extreme upper limit of travel of the piston and the stem beingprovided with a shoulder for engaging an element of thesupport to fixthe extreme lower limit of travel of the piston, adjustable means on theplunger for fixing the upperlimit of travel of the piston to any limitlower than the extreme limit, said cylinder being provided atits headnear the edge thereof with an aperture for admitting fluid to thecylinder, a rotatably mounted member closely fitting on the cylinderhead and having-a central opening and an eccentric recess communicating:with the opening and aperture, whereby uponrotation of the member theretarding force of the dash-pot maybe fixed to any predetermined valueand thus determine the timelimit of thedropping of the plunger, and

control switches actuated by the dropping of the plunger.

6. A fluid controlled time-limit device for a control relay having amovable core, including a cylinder having a head, a loosely fittingpiston in the cylinder operated by the core, the head being providedwith an eccentric aperture for the admission of the retarding fluid, acup-shaped member hav-' ing a central opening and an eccentric recesscommunicating with the opening and the aperture rotatably mounted on thehead and snugly fitting thereon whereby upon rotation of the cup-shapedmember the timelimit of the relay may be accurately adjusted, thecylinder having an opening in the side wall thereof and so positioned toeliminate any retardation of the core near its lower limit of travel,and screens over the central opening of the cup-shaped member and theopening in the side wall of the cylinder.

7. A time-limit control relay for an electric device including aplunger, a main coil for raising the plunger, an auxiliary coil adaptedto be connected in the load line of the electric device to be controlledand designed to prevent complete de-energization of the relay uponde-energization of the main coil, whereby the dropping of the plunger isretarded by a force proportional to the load current of the electricdevice, means on said relay for varying the flux distribution thereof, afluid-controlled dashpot for further retarding the dropping of theplunger upon de-energization of the main coil, means for adjusting theretarding force of the dash-pot to fix, for any value of current in theauxiliary coil, to an desired time interval the dropping 0 the plunger,and control switches actuated by the dropping of the plunger.

In testimony whereof, I have hereunto subscribed my name this 24th dayof October, 1929.

PATRICK C. WARD.

